The invention relates to a procedure for manufacturing sterile containers of plastic material and a system for using it.
It applies most particularly to the manufacturing of sterile containers using preforms which are heated to bring them to their molding temperature (i.e., to a temperature at which the plastic material is softened), then introduced into a finishing mold where the final container is obtained by blow molding or drawing/blow molding of the preform.
One especially advantageous application is in line systems or even in combined systems (also called monobloc) for the manufacturing, filling and sealing of the containers in which the sterile containers are bottled, then capped immediately after their manufacture.
A combined or monobloc system is described in the French patent 74.37155 in the name of Socixc3xa9txc3xa9 des Machines pour la Transformation des Plastiques: in this type of system, the manufacturing, the filling and the sealing of the containers takes place in one enclosure bathed in a flow of sterile air.
The patent U.S. Pat. No. 3,809,768 describes a line system, i.e., a system in which each part, having a specific function, is distinct from the others, and a sterile environment is maintained in each of the parts and, naturally, at the time of transfer between two successive parts.
In order to obtain sterile containers, various solutions have been considered.
One solution consists in sterilizing or decontaminating the containers before their manufacture, for example, by filling them with or immersing them in an appropriate sterilizing solution. This idea presents the following disadvantages:
1) First of all, after filling or immersion, it is necessary to drain the containers, possibly rinse them with a rinsing solution, then to dry them since the final contents of the container could be denatured by the sterilizing solution (or decontaminating solution), or the rinsing solution if the latter is used.
Thus, this solution is hard to use with an in-line filling system because of the time that it requires to use it.
2) In addition, after draining the containers, it is necessary to recover the sterilizing or decontaminating solution, the same is true with the rinsing solution, and to recycle it (them). In fact, it is not possible to imagine throwing the solution(s) away after a single use because of the considerable consumption that this would involve. Thus, it is necessary to provide a recycling system for each solution used. This creates systems that are very complicated and costly.
In addition, from the psychological point of view, the user may question the quality of the recycling.
Another solution consists in sterilizing the preforms before introducing them into the machine for manufacturing containers. In order to do this, the preforms are filled with a sterilizing/decontaminating solution by soaking or filling and maintained in contact with the solution for a certain period of time; the preforms are then drained and the traces of the solution are removed before the preforms are introduced into the heating furnace in preparation for blow molding them.
This solution presents the following disadvantages:
1) On one hand, the contact time between the sterilizing solution and each preform must be long (typically more than one minute with hydrogen peroxide (H202) and again the quality of the sterilization is variable from one preform to another), which involves a sterilizing system of significant complication to maintain the elevated production rates that are classically found in the blow molding or drawing/blow molding system;
2) The sterilizing system must be connected to the heating system by a sterile tunnel;
3) The draining of the preforms after sterilizing/decontaminating implies, as in the case of containers, collection of the cleaning solution and recycling it in a connected device.
The goal of the invention is to remedy the inconveniences of the type mentioned above by proposing a process and a system that is compatible with the high production rates of blow molding and which would be of minimum complication, naturally while still being efficient.
According to the invention, a procedure for obtaining a sterile container starting from a preform of thermoplastic material which is heated then blow molded or alternatively drawn and blow molded, is characterized in that it consists of 1) applying a sterilizing product that is activated by heat to the said preform, and 2) heating the said preform to simultaneously activate the said fluid and increase the temperature of said preform in order to reach the molding temperature, and 3) blow molding, alternatively drawing and blow molding the preform, to obtain the final container.
Thus, in heating the preform for simultaneously activating the sterilizing product and increasing the temperature of the preform in order to reach its blow molding temperature, a single operation is used to carry out the sterilizing and the softening of the material that makes up the preform in order to have it ready for blow molding. Thus the entire cycle is shortened.
In this way, it is no longer necessary to provide a special system for sterilizing since a common system is used for heating for the purposes of activating a sterilizing product and for softening the preform. Providing the means to apply the product to the preforms is sufficient.
In addition, there is an energy savings.
The operational safety of the sterilization is complete since the containers are blow molded immediately after the preforms have been sterilized: since the preforms are sterilized while being heated and the temperature at which they are introduced into the molds, then blow molded, is such that new germs cannot develop.
With the procedures of the previous type, according to which the preforms are sterilized, dried and transferred to the furnace, there exists a risk of pollution of the preforms during the transfer, for example if the sterile tunnel has a defect. This type of risk is eliminated here.
In addition, with the procedure according to the invention, the activation of the product by heat results in keeping the elements in contact with the preforms sterile at least in the heating zone. Thus it is not necessary to provide a flow of sterile air in this zone.
According to another characteristic, the application of the sterilizing product is proceeded by a phase of suppressing static electricity in the preform.
Thus, the particles and germs are more easily treated as a result since they are detached from the wall of the preform.
According to another characteristic, the product is a fluid and its application is carried out by wetting the preform.
Surprisingly, it has in fact been confirmed that it is not necessary to introduce large quantities of the product for sterilizing the preforms and that a simple wetting is adequate.
In one type of embodiment, the wetting is carried out when the preform enters the system upstream of the heating means by spraying the necessary quantity of the fluid into the preform in such a way as to moisten at least its entire interior surface.
In another method of embodiment, the wetting is carried out by filling the preform and then draining it without drying it before it is brought into the heating means.
This other method of embodiment presents the advantage, in comparison to the procedure that is the state of the art mentioned at the beginning, of requiring a recycling system of lesser performance since it is essential that the decontamination take place at the time of heating. The product of the draining is thus only slightly contaminated.
According to another characteristic, the quantity of the product placed in the preform is such that not just the preform leaves the heating means in a sterile condition, but all of the product evaporates at the time of heating, which avoids disturbances in the molding phase of the final container. In fact, traces of the product could be detrimental in obtaining proper molding.
In one method of embodiment, the final blow molding is carried out using air that is sufficiently filtered in order not to reintroduce undesirable particles.
Thus, it is possible to use a classic blow molding system with appropriate filters.
In another embodiment, the final blow molding is carried out using sterile air.